1. Field of the Invention
Aspects of the present invention relate to an optical pickup which records and/or reproduces information onto and/or from a disc type optical information storage medium. More particularly, aspects of the present invention relate to an optical pickup actuator and an optical recording and/or reproducing apparatus having the same.
2. Description of the Related Art
An optical recording and/or reproducing apparatus is provided with an optical pickup which records optical information on or reproduces the recorded optical information from an optical recording medium by irradiating a laser beam onto the optical recording medium, such as a compact disk (CD), a digital versatile disk (DVD), etc.
The optical pickup requires an objective lens, which focuses an incident light to the optical recording medium, and an actuator, which drives the objective lens in a focusing direction and a tracking direction.
The actuator includes a base, a lens holder on which the objective lens is mounted, and a magnetic circuit for driving the lens holder in the focusing direction and the tracking direction, while supporting the lens holder to move with respect to the base.
The magnetic circuit includes focusing coils driving the objective lens in the focusing direction, tracking coils driving the objective lens in the tracking direction, and magnets installed, facing the coils for interactions. The actuator drives the focusing coils and the tracking coils independently to control movement of the objective lens in the focusing direction and the tracking direction.
In recent years, attention has been focused on developing and establishing a standard for DVDs holding a large amount of data (greater than 4.7 GB per side) and high definition (HD)-DVDs having higher density than the 4.7 GB and capable of recording high definition moving images (greater than 23 GB per side). In case of the high-density optical recording medium, the thickness of an optical recording medium needs to be reduced as the NA (numerical aperture) of an objective lens is increased. For instance, although the thickness of a conventional CD is about 1.2 mm, the thickness of a conventional DVD is about 0.6 mm. Thus, it is highly possible that a next generation HD-DVD may be as thin as about 0.1 mm.
However, as the rotation speed increases, the high-density, thin optical recording medium generates eccentricity problems due to manufacturing errors. As a result of the eccentricity, the optical recording medium may not rotate parallel to a plane, but may deformed in a direction transverse to the plane.
Since focusing control and tracking control of an objective lens in corresponding directions are not sufficient to accurately focus a light to a recording side of an optical disk, there is a need to develop an actuator, which is capable of driving the objective lens not only in the tracking direction, but also in the focusing and tilting directions.